1. Field of the Invention
The present invention relates to a dry granulated product containing L-lysine as a main component. L-lysine is useful as an additive for animal feed and so forth.
2. Description of the Related Art
Since an additive for animal feed containing an amino acid as a main component is not required to be purified so much when it is used as an additive for feed, it has been attempted to produce such an additive by directly drying a fermentation solution in which an amino acid is accumulated (Japanese Patent Laid-open Publication (Kokai) Nos. 59-169454 and 5-192089). According to Japanese Patent Laid-open Publication No. 5-192089, it is pointed out that, in additives for animal feed obtained in such a manner, free amino acid content is more reduced in a dry product containing a basic amino acid as a main component compared with a dry product containing a neutral amino acid as a main component. It is considered that this is caused partly because anions are added to a culture broth during the culture for the production of a dry product containing a basic amino acid as counter anions of the basic amino acid to maintain electric neutrality of the culture broth, and the presence of the anions in the dry product results in the reduction of the amino acid content. This problem is also observed for L-lysine, which is one of basic amino acids.
Use of crystals or dry product of L-lysine base not containing counter ions at all as an additive for animal feed may be conceived in order to improve L-lysine content in the solid matter. However, L-lysine base suffers from a problem that it shows marked hygroscopic property and caking property, and thus its handling is difficult.
As a method of improving hygroscopic property and caking property of a dry product, for example, a method of adding an anticaking agent is contemplated as disclosed in Japanese Patent Laid-open Publication No. 9-28310. However, addition of anticaking agent results in reduction of content in the final product and further it is also economically disadvantageous.